The fastening of transmitters and receivers of optoelectronic physiological sensors onto the skin surface is very problematical. Even the slightest movements of the parts of the sensor relative to the skin surface lead to numerous artifacts (structures in a fixed cell or tissue formed by manipulations or by the reagent), and thus, lead to signal fluctuations. To avoid these movements, both the transmitter and the receiver need to be tightly pressed onto the skin surface.
Tight pressing can disturb the circulation of the blood through the capillary bed, which disturbance can also lead to erroneous measurements and recordings. A slighter inclination to the formation of artifacts simultaneously with higher signal quality cannot be attained with flexible or resilient clamps on the skin, or by means of elastic strips and the like.
Because of this, it has been suggested (see, e.g., European Patent 0 127 947 A2) to affix a light-impermeable strip to the support layer for the transmitter and receiver. The strip, in the area of the light outlet surface of the transmitter and in the area of the light admission surface of the receiver, has an opening for each. This strip is affixed to a sheet of clear polyester, coated on both sides with an adhesive material. Also, a porous protective layer can be affixed to the reverse side of the light impermeable layer supporting the transmitter and receiver members. Despite this costly construction of the transmitter and of the adhesive connection between the transmitter and the skin surface, the signal quality is still inadequate.